Typically, the DNA is separated into individual genes and replicated many times in a number of 96 well plates (an industry standard) and minute pieces of DNA are positioned on an underlying substrate such as a chip from the DNA genes solubilized in a solution. After forming the DNA wet array and drying the DNA, the completed array is bathed in a solution of two or more fluoresces labeled total genomic tags, with the tags hybridizing to bind to a particular gene on the array by causing the fluoresces to fluoresce and by measuring the intensity of the signals, determinations may be made between the various features.
To date, the creation of such array is complicated, and while arrays have envisioned in terms of several thousand features per substrate area, such arrays are produced in terms of days rather than minutes. Further, while the well plates can store the individual genes within respective wells, over time the machine forming the wet arrays requires constant cleaning to deter contamination of the arrays. Once created, such gene chips are useful in testing for dozens of genetic diseases of different severity, and the test can be cheaply and quickly effected. Chips have been produced; however, significant energy is required to realize a practical chip.
Aeffymetrix, Inc. has recently disclosed an approach utilizing a glass slide as a substrate, about half the size of a postage stamp with thousands of distinct microscopic squares (features), each attesting for a specific DNA sequence. The features on the glass surface are covered with a compound containing chemical protecting groups that block further chemical reaction. Optically, collected protecting groups can be removed. A thin mask is then pulled over the chip containing holes to allow light to strike specific features, with the other features on the chip remaining protected. Subsequently, the chip is washed with a solution containing one of four DNA components called nucleotides (A, C, G or T). The DNA component washed solution binds only to the unprotected features. Each incoming nucleotide carries its own protecting group so that the washed features are reprotected. Sequentially, a new mask with different pattern of holes and optical (light) impingement removes the protecting groups at the different pattern of holes associated with a second group of features. In a multi-cycle process, chains of precisely ordered nucleotides are built onto each feature.
As may be appreciated, genes are made of two strands of DNA nucleotides of a specific order, bound to each other like the halves of a zipper. Nucleotide binding is governed by certain relationships. For instance, the nucleotide T always binds with that of A, but never with C or G, or with another T. Thus, a strand of nucleotides has a single complimentary strand which will match it and bind exactly. Thus, a chip (or other substrate) containing nucleotide strands of a given composition can find specific mutations in a person's genes. Man has approximately 80,000 genes. Therefore, a DNA gene array of closely spaced features or dots of microscopic size may be constituted by as many as 400,000 dots on a single substrate and capable of carrying all DNA's for several persons, or one person in redundancy.
In the production of the liquid DNA gene arrays, DNA is extracted typically from tissue cells grown in cultures, the DNA is fragmented into thousands of pieces which can be chemically labeled with a fluorescent compound. The pieces contain parts of genes or whole genes. Thus, each feature of a chip contains a nucleotide strand of a normal or mutant section of a known gene. Thus, all possible mutations of a gene can be detected by features on a single chip and all may be tested simultaneously. By use of an optical scanner, the features on the chip can be read for fluorescent color and intensity. Features containing fluorescently labeled DNA may provide signals fed to a computer as input data, with that data being analyzed to provide information as to whether the person providing the genes carries one or more mutations, and further the identification of the mutation itself.
It is therefore a primary object of the present invention to provide a high throughput test system and components for ascertaining genetic mutations enhanced by the dry, orderly world of computer hardware in contrast to the wet and messy world of living tissue and of liquid DNA gene features applied to the slide by effecting a dry DNA transfer film to create in turn, a dry DNA analyzing array of features or spots on such slide.